There are many different situations in which two shafts are mechanically coupled together so that the shafts rotate in unison with each other. Furthermore, there are many different ways of mechanically coupling the shafts together.
For example, in some situations an endless belt or chain is mechanically coupled to a pulley or sprocket, respectively, attached to the two rotatable shafts. Consequently, with the belt or chain disposed around the pulleys or sprockets, the two shafts rotate in unison with each other.
In other situations, the shafts are directly mechanically connected together. For example, a gear wheel may be attached to each of the rotating shafts so that each gear wheel rotates in unison with its associated shaft. The gear wheels are dimensioned and positioned so that they mesh with each other. Consequently, rotation of one shaft rotatably drives the other shaft and vice versa.
The foregoing is by way of example only. There are many different ways to mechanically connect two rotating shafts together so that the shafts rotate in unison with each other, i.e. are rotationally coupled, whether at the same speed or at different speeds.
The primary disadvantage of these previously known means for mechanically coupling two rotating shafts together, however, is that energy is lost in the mechanical connection so that the transmission of energy or power from one shaft to the other shaft is less than 100%, and oftentimes much less than 100%. A major cause of this energy loss is created by the friction inherent in these previously known mechanical connections. These frictional losses, in turn, generate heat which, after a prolonged time or during high-speed operation, can even result in destruction of the coupling from warpage and other material breakdown in the mechanical connection.